title: Risk of cholecystitis in patients with cancer: a population-based cohort study in Denmark.
abstract: BACKGROUND
  To the authors' knowledge, little information is available regarding the incidence of cholecystitis among patients with cancer.
  
  
  METHODS
  The authors conducted a population-based historical cohort study of 51,228 patients with incident cancer, identified in medical databases of western Denmark between 1995 and 2003. A general population comparison cohort of 512,280 persons was assembled using the Danish Civil Registration System. The occurrence of cholecystitis in the 2 groups was determined by linkage to the regional Hospital Discharge Registry.
  
  
  RESULTS
  In all, 230 incident diagnoses of cholecystitis were identified in the cancer cohort during 130,185 person-years (median follow-up time: 1.6 years), corresponding to an incidence rate of 1.8 of 1000 person-years. After adjustment for confounders, the relative risk (RR) for cholecystitis among cancer patients compared with the general population cohort was 1.38 (95% confidence interval [95% CI], 1.20-1.58). Overall, the RR for cholecystitis was doubled during the first 6 months after cancer diagnosis (RR = 1.95; 95% CI, 1.50-2.54), after which the RR declined but remained greater than 1 throughout the rest of the follow-up period (RR = 1.23; 95% CI, 1.05-1.45). Cancer patients between the ages of 51 and 70 years had the highest risk increase for cholecystitis compared with other age groups. During the first 6 months after a cancer diagnosis, pancreatic cancers (12 cholecystitis events; RR = 9.44 [95% CI, 5.18-17.18]) and colorectal cancers (10 cholecystitis events; RR = 4.98 [95% CI, 2.65-9.34]) were found to be associated with the greatest cholecystitis risk increase compared with other tumor types. After 6 months, most cancers were associated with a relatively small increased risk, although there was an RR of 4.72 (95% CI, 1.99-11.21) based on 5 cholecystitis events among thyroid cancer patients.
  
  
  CONCLUSIONS
  The results of the current study indicate that cholecystitis occurs more frequently among cancer patients than in the general population, particularly within the first 6 months after a cancer diagnosis. Clinicians who treat cancer patients should remain vigilant about this type of infection.
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Aalborg, Denmark. r.thomsen@rn.dk
authors.forename: Reimar W
authors.initials: RW
authors.lastname: Thomsen
authors.forename: Henrik F
authors.initials: HF
authors.lastname: Thomsen
authors.forename: Mette
authors.initials: M
authors.lastname: Nørgaard
authors.forename: Karynsa
authors.initials: K
authors.lastname: Cetin
authors.forename: Joseph K
authors.initials: JK
authors.lastname: McLaughlin
authors.forename: Robert E
authors.initials: RE
authors.lastname: Tarone
authors.forename: Jon P
authors.initials: JP
authors.lastname: Fryzek
authors.forename: Henrik T
authors.initials: HT
authors.lastname: Sørensen
mesh_terms: D000368:Aged; D002764:Cholecystitis / Q000150:complications* / Q000453:epidemiology; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000150:complications*; D044382:Population Groups; D018570:Risk Assessment